Delivery of implantable therapeutic devices by less invasive means has been demonstrated to be desirable in numerous clinical situations. For example, vascular embolization has been used to control vascular bleeding, to occlude the blood supply to tumors, to occlude fallopian tubes, and to occlude vascular aneurysms, particularly intracranial aneurysms. In recent years, vascular embolization for the treatment of aneurysms has received much attention. As another example, the use of mesh or scaffold devices such as stents to open blocked vessels or to retain embolic coils have also received much attention.
Several different treatment modalities have been employed in the prior art for deploying implant devices. For example, numerous repositionable detachment systems for implant devices have been described in the prior art including U.S. Pat. No. 5,895,385 to Guglielmi et al. and U.S. Pat. No. 5,108,407 to Geremia et al., the contents of which are hereby incorporated by reference. Several systems, such as those disclosed in U.S. Pat. No. 6,500,149 to Gandhi et al. and U.S. Pat. No. 4,346,712 to Handa et al., the contents of which are hereby incorporated by reference, describe the use of a heater to detach and deploy the implant device.
Some percutaneously delivered detachable implant systems, such as those used to deliver occlusive coils to aneurysms, include a detachable implant that is temporarily attached to a pusher mechanism within a microcatheter. The pusher mechanism is used to advance the implant out of the distal end of the microcatheter. Once the implant has been advanced to a desired location relative to the microcatheter, referred to herein as a detachment zone, a detachment mechanism is employed to detach the implant from the pusher. It is important not to detach the implant prior to reaching the detachment zone as the implant may get hung up in the end of the catheter and subsequently get deployed at an undesirable location in the body.
Typically, in order to determine whether the implant has been advanced to the detachment zone relative to the microcatheter, radiopaque markers are used on both the microcatheter and either the pusher, the implant, or both. Thus, an operator uses the radiopaque markers to monitor the relative positions of the microcatheter and the implant as the implant is being advanced with the pusher. Monitoring the positions of the radiopaque markers requires the use of an x-ray device during the procedure. Using an x-ray imaging machine adds expense, complicates the procedure, and adds another space-consuming machine to the area surrounding the patient. Additionally, due to the coiled nature of the implant, the view of the radiopaque markers can become blocked by the coil.